Mid-Holocene deepening of the Southeast Pacific oxycline
"This study presents new high resolution sedimentary δ15N records from piston cores collected within and outside the present-day eastern south Pacific oxygen minimum zone along a latitudinal transect from 3.5°S to 15°S. Radiocarbon dating of foraminifera and organic matter show that the cores cover the Holocene and the last deglaciation with high sedimentation rate allowing interpretations at millennial to centennial timescale. [...]"
Source: Global and Planetary Change
Authors: Elfi Mollier-Vogel et al.
Effects of Higher CO2 and Temperature on Exopolymer Particle Content and Physical Properties of Marine Aggregates
"We investigated how future ocean conditions, and specifically the interaction between temperature and CO2, might affect marine aggregate formation and physical properties. Initially, mesocosms filled with coastal seawater were subjected to three different treatments of CO2 concentration and temperature: (1) 750 ppm CO2, 16°C, (2) 750 ppm CO2, 20°C, and (3) 390 ppm CO2, 16°C. Diatom-dominated phytoplankton blooms were induced in the mesocosms by addition of nutrients. [...]"
Source: Frontiers in Marine Science
Authors: Carolina Cisternas-Novoa et al.
Isotopic fingerprints of benthic nitrogen cycling in the Peruvian oxygen minimum zone
"Stable isotopes (15,14N, 18,16O) of dissolved inorganic nitrogen (N) were measured in sediment porewaters and benthic flux chambers across the Peruvian oxygen minimum zone (OMZ) from 74 to 1000 m water depth. Sediments at all locations were net consumers of bottom water NO3−. In waters shallower than 400 m, this sink was largely attributed to dissimilatory nitrate reduction to ammonium (DNRA) by filamentous nitrate-storing bacteria (Marithioploca and Beggiatoa) and to denitrification by foraminifera. [...]"
Source: Geochimica et Cosmochimica Acta
Authors: A.W.Dale et al.
‘Stop treating seas as a sewer,’ MPs urge in bid for protection treaty
Plastic pollution is set to treble in the next decade, the environmental audit committee warned, while overfishing is denuding vital marine habitats of fish, and climate change is causing harmful warming of the oceans as well as deoxygenation and acidification. [...]"
Source: The Guardian
UK must support ‘Paris agreement for the sea’ to protect global oceans, say MPs
Besides pollution, climate change, overfishing and deep sea mining are all threatening marine ecosystems and the trillions of pounds they deliver to the economy, the report states. [...]"
How fast are the oceans warming?
"Climate change from human activities mainly results from the energy imbalance in Earth's climate system caused by rising concentrations of heat-trapping gases. About 93% of the energy imbalance accumulates in the ocean as increased ocean heat content (OHC). The ocean record of this imbalance is much less affected by internal variability and is thus better suited for detecting and attributing human influences than more commonly used surface temperature records. Recent observation-based estimates show rapid warming of Earth's oceans over the past few decades (see the figure). [...]"
Authors: Lijing Cheng et al
Deglacial to Holocene Ocean Temperatures in the Humboldt Current System as Indicated by Alkenone Paleothermometry
"The response of the Humboldt Current System to future global warming is uncertain. Here we reconstruct alkenone‐derived near‐surface temperatures from multiple cores along the Peruvian coast to infer the driving mechanisms of upwelling changes for the last 20 kyr. Our records show a deglacial warming consistent with Antarctic ice‐core temperatures and a Mid‐Holocene cooling, which, in combination with other paleoceanographic records, suggest a strengthening of upwelling conditions. [...]"
Source: Geophysical Research Letters
Authors: Renato Salvatteci et al.
Oxygen variability controls denitrification in the Bay of Bengal oxygen minimum zone
"Nitrate limits productivity in much of the ocean. Nitrate residence time is a few thousand years and changes in nitrate loss could influence ocean productivity. A major sinks for nitrate is denitrification and anaerobic ammonia oxidation in the oxygen minimum zones (OMZs). The Bay of Bengal OMZ is anomalous because large amounts of nitrate loss do not occur there, while nitrate is removed in the nearby OMZ of the Arabian Sea. Observations of nitrate and oxygen made over 5 years by 20 profiling floats equipped with chemical sensors in the Bay of Bengal and the Arabian Sea are used to understand why nitrate is removed rapidly in the Arabian Sea, but not in the Bay of Bengal. [...]"
Source: Geophysical Reasearch Letters
Authors: Kenneth S. Johnson, Stephen C. Riser and M. Ravichandran
Effects of Coastal Upwelling and Downwelling on Hydrographic Variability and Dissolved Oxygen in Mobile Bay
"Upwellling and downwelling events are important coastal processes that strongly influence shelf ecosystem dynamics. Though changes on the shelf have been well studied, the impact of these events on estuarine systems has received less focus. In summer 2016 a downwelling and upwelling event were observed near the mouth of Mobile Bay. The impact of these events were examined throughout the bay with high spatial resolution observations. Five boat surveys were conducted to capture the spatial response of offshore forcing and its changes in the estuary. In addition to the surveys, 16 CTDs were deployed and measured temporal changes. [...]"
Source: JGE Oceans
Authors: Jeffrey Coogan, Brian Dzwonkowski and John Lehrter
Southern Hemisphere sea-surface temperatures during the Cenomanian–Turonian: Implications for the termination of Oceanic Anoxic Event 2
"Mesozoic oceanic anoxic events (OAEs) were major perturbations of the Earth system, associated with high CO2 concentrations in the oceans and atmosphere, high temperatures, and widespread organic-carbon burial. Models for explaining OAEs and other similar phenomena in Earth history make specific predictions about the role and pattern of temperature change, which can be tested through comparison with the geological record. Oceanic Anoxic Event 2 (OAE 2) occurred ~94 m.y. ago and is commonly considered as the type example of an OAE. [...]"
Authors: Stuart A. Robinson et al.